1. Field of the Invention
The invention relates to computer systems having audio equipment associated therewith and, more particularly, to an audio coder/decoder having a digital signal processor interface.
2. Description of Related Art
In the past, interfaces between a computer system and audio equipment associated therewith were not configured to provide signal processing capability. For example, a typical prior art interface between a computer system and audio equipment may be seen by reference to FIG. 1. Here, an audio coder/decoder 10 which includes a data memory access (or "DMA") interface 12, a digital-to-analog (or "D/A") converter 14 and an analog-to-digital (or "A/D") converter 16 provides the interface between an industry standard architecture (or "ISA") bus 18 of a computer system (not shown) and audio equipment which includes a speaker 20 and an analog input 22, for example, a microphone.
Digital audio signals which, for example, may be propagated by a memory subsystem (not shown) associated with the computer system onto the ISA bus 18, are transmitted from the ISA bus 18 to the DMA interface 12 via an audio data bus 24, most commonly a parallel bus for simultaneously transferring multiple data bits. Digital data input the DMA interface is converted from parallel to serial by a parallel to serial converter (not shown) and transferred to the D/A converter 14. There, the digital serial data is converted into analog and then transmitted to the speaker 20 for audio transmission. Analog audio signal are transmitted by the microphone or other analog input 22 to the A/D converter 16. Here, the analog audio signals are converted into serial digital audio data and transmitted to the DMA interface 12. The DMA interface 12 converts the serial digital audio data into parallel data and transmits the parallel digital audio data to the ISA bus 18 via the data bus 24.
Interfaces between a computer system and associated audio equipment such as the interface illustrated in FIG. 1 are not configured to process the data being output to or input from the audio equipment For example, various data compression techniques have been utilized to compress information encoded in the form of digital data to an abbreviated or shorthand form so that the number of data bits which must be utilized in order to store the encoded information in memory or transmit the encoded information to a selected destination is reduced Typically, a data compression algorithm involves identifying redundant or unnecessary information and substituting an abbreviation or shorthand symbol for that information and the use of such data compression algorithms to reduce the number of bits required to store or transmit data are common.
In order to provide signal processing capability for input and/or output audio signals for an audio interface such as that illustrated in FIG. 1, a digital signal processor would be connected directly to the ISA bus 18. Digital audio signals being transmitted to the DMA interface 12 would first be routed by the ISA bus 18 to the DSP for processing and then returned to the ISA bus 18 for routing to its final destination. As such a configuration would add two bus exchanges for every data transfers to the DMA interface 12, traffic on the ISA bus 18 would increase dramatically. Furthermore, the additional glue logic required in order to permit the DSP to interface with the ISA bus 18 would increase the cost of such a computer system.